This invention relates to a fire or smoke detector comprising a detector head and a socket plate, and more particularly to a fire or smoke detector wherein the detector head and the socket plate are provided with an improved coupling mechanism.
A detector which serves as a transmitter for transmitting a fire or smoke detection signal, generally comprising a socket plate secured to a ceiling or the like and a detector head assembly for a detector unit including a detecting section and an electric circuit thereof. Metal coupling terminals are respectively provided to the socket plate and the detector head, so that the detector head is fittingly plugged into the socket plate in a relation that a subsequent rotation therebetween can be carried out to lockingly couple each other. Accordingly, in the case where signal lines from a receiver are connected to the metal coupling terminals of the socket plate, both an electrical connection between the receiver and the detector head and a coupling function between the socket plate and the detector head can be achieved by an engagement of the metal coupling terminals.
Generally, these detectors are classified into an ionization type smoke detector, a photoelectric type smoke detector, a rate of raise type heat detector, a fixed temperature type heat detector and the like in view of a subject to be detected or an operation method thereof. These devices becomes required safety equipment in homes as well as commercial areas. A socket plate which is commonly used with the above described types of detector heads, has been required in recent designs. That is, the engaging position of the metal coupling terminals is identical regardless of the kinds of detector heads so that each kind of detector head can be lockingly coupled to the common socket plate. However, it is necessary to select a suitable detector applicable to the location where the detector is to be utilized. For example, in view of a probability of explosion, a fire detector having an electric switch or a breaking point cannot be employed in the place where an explosive material is stored. Furthermore, a smoke detector cannot be employed in the place where dust scattered in the air exceeds allowable ranges. Accordingly, the required detector is selected such that a suitable detector head designated according to the circumstances need be merely coupled to the corresponding socket plate. In this case, however, because such designation is usually accomplished in a planning step, a possibility exists of an erroneous coupling during actual construction and installation. Furthermore, it should be noted that a possibility also exists of an erroneous coupling where a different kind of detector head is coupled to the socket plate, in the case where after the detector head is removed from the corresponding socket plate during maintenance and inspection thereof, the removed detector head is again coupled.